If one or more of these directories exist, the requirements for their
contents are the same as the normal /lib directory, except that
/lib<qual>/cpp is not required.[footnote 13]

[12]This is commonly used for 64-bit or 32-bit support on systems which
support multiple binary formats, but require libraries of the same name.
In this case, /lib32 and /lib64 might be the library
directories, and /lib a symlink to one of them.

[13]/lib<qual>/cpp is still permitted: this allows the case where
/lib and /lib<qual> are the same (one is a symbolic link
to the other).